Disclosed herein is a vital information measurement device and a vehicle seat, and particularly, a vital information measurement device having the function of measuring vital information of a subject, which may be a human or an animal, and a related vehicle seat.
In recent years, for the purpose of promptly reporting, to a driver, that a driver's physical condition is changed while a vehicle is running, various vehicle seats configured to be able to display a change in physical condition by detecting various parameters indicating the state of the driver have been proposed.
For example, Japanese Patent Document No. 2009-50679 A (“the '679 Document”) discloses an electrocardiogram measurement device including first and second electrodes serving as two sensors optionally arranged at a seat back and a ground electrode disposed in a seat cushion and configured to determine a reference potential.
In this electrocardiogram measurement device, an electric signal associated with an electrocardiogram detected from a driver by two sensors is efficiently sensed in such a manner that the electric signal is amplified by a two-stage amplifier, and therefore, the health condition of the driver can be determined.
Japanese Patent Document No. 2007-301175 A (“the '175 Document”) discloses a measurement device including planar electrodes serving as a plurality of sensors arranged respectively at the positions contacting the back of a driver, the region extending from the waist to the hip of the driver, and the thighs of the driver.
In this measurement device, one of the sensors is provided for obtaining the neutral-point potential of an amplifier. This reduces signal noise, and therefore, abnormality can be determined in such a manner that a heart-rate signal and a respiration signal from the driver are suitably detected.
Sheet-shaped sensors are broadly used as the sensors of the above-cited references. Each sensor mainly includes a conductive line configuring a sensor body, and a conductive sheet fixing the conductive line. These sensors are arranged in a part of the seat back supporting the back of the seated passenger.
The sheet-shaped sensor of this type might receive a compressive load when the seated passenger leans on the seat back, resulting in wrinkling caused due to partial overlapping of the sheet-shaped sensor. As a result, there is a possibility that signal noise is caused or that the conductive line deforms due to repeat load application.
However, in the vehicle seat including the vital information measurement device as described in the above-cited references, reduction in occurrence of wrinkling of the sheet-shaped sensors has not been taken into consideration.
For this reason, vehicle seats have been demanded which include sheet-shaped sensors which can stably detect vital signals from seated passengers/subjects and which improves durability against repeat load application.